spider bot? any biologists out there that no how there legs work?
Is there any reason other then cost why all the robot spider kits are hexapods(6 legged)?
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Post Edited (mctrivia) : 4/10/2010 2:00:22 AM GMT
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Post Edited (mctrivia) : 4/10/2010 2:00:22 AM GMT
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I've seen some mechanical Lego designs that have eight legs powered by two motors, but I assumed that was a fallout of their gear trains and not a design goal.
I was just wondering because real spiders have 8 legs. Though I guess most kits only have 1 joint in the middle of the leg and it looks like mos of the real ones have 2. So maybe realism is just to expensive and complicated.
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1. allow them to climb on their web easier without breaking it
2. increase attacking ability with 6 back legs doing the walking and the 2 front attacking.
Also--nice to see you moved from web spider to robot! I think you should make it 8 legged just to see if you can mimic a spiders attack stance.
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Pi aren't squared, pi are round. Cornbread are squared!
3 deg of freedom * 6 legs =18 servos
3 deg of freedom * 8 legs =24 servos
I do like the idea of having 8 legs like a real spider though.
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Pi aren't squared, pi are round. Cornbread are squared!
Those servos do not have the torque needed. Once I figure out the mass of the body parts I should be able to figure out how much torque is needed. hopefully under $10 servo will do.
Thanks for the complement. I like my new site to. Looks cool and the built in inventory system makes my life a lot easier. Now if only I could get it to assemble, and ship the stuff for me also.
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Pi aren't squared, pi are round. Cornbread are squared!
The front two legs could also be multipurpose rather than just for locomotion.
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Hobbycity.com has some very inexpensive servos. If I remember correctly, $4 buys a servo comparable to the HS-55. I used them in delta wing combat [noparse]:)[/noparse]
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"puff"...... Smile, there went another one.
Cool idea!
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Current sensing on servos should be effective force feedback method right
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Pi aren't squared, pi are round. Cornbread are squared!
i realised I can make both designs reasonably:
ant:
*6 legs, 3 servos/leg
*head, 5 servos
*body, 2 servos
25 total
spider:
*8 legs, 4-6 servos/leg
*head, 2 servos
*body, 2 servos
38-54 servos total
since they both would use the same servos and controlers(though the spider would need 2 controlers)
one thing I have been having some trouble with though is figuring out how the legs of the spider works:
shows that there are 11 muscles in the spiders legs
i. Extensor trochanteris, ii. Flexor trochanteris; iii. Flexor longus femoris; iv. Flexor bilobatus femoris; v. Flexor bilo- batus patellae ; vi. Flexor patellae ; vii. Protractor tibiae ; viii. Flexor tibiae : ix. Flexor metatarsi ; x. Extensor tarsi ; xi. Flexor tarsi.
shows that there are 8 parts to the leg:
1. coxa
2. trochanter
3. femur
4. patella
5. tibia
6. metatarsus
7. tarsus
8. tarsal claws
I think the muscles work as follows:
i,ii: provide left/right movement of the trochanter
iii,iv provides up/down movement of the femur
v,vi: provide up/down movement of the patella
vii,viii: provide left/right movement of the tibia
ix: up/down movement of the metarsus
x,xi: up/down movement of the tarsus
but this would mean i need 6 servos/leg. also i can't find any images showing the legs in any possition but straight(contradicting my vii,viii asumption) and the patella and tibia always seem to be straight like they are fused. that would make only 4 servos needed.
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Post Edited (mctrivia) : 4/9/2010 10:24:55 PM GMT
Jim-
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Treat i,ii,iii, iv as the hip joint: It needs up/down and forward/back
Treat v, vi, vii, viii as the knee joint. You really only need flexion/extension since the knee does not abduct/adduct(right/left)
Treat ix, x, xi as the ankle/toes. Similar to knee joint. Only flexion/extension needed. The ankle and foot have very little lateral movement
My first impression was that the algorithm could be improved for walking. Second, eight legs makes for a lot more work to move the same distance as say a hexapod. Also with eight legs there is not much room to move laterally at the hip joint given the arrangement of the legs.
Maybe for standard flat surface motility, use only six legs. The question is, under what situations are eight legs better than six. If the front two legs were longer than the others, they could be used for climbing, for example. They would be more like arms than legs.
I could not find any video of slow motion spider locomotion.
Real spiders can sacrifice legs to escape.
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Check out the sample vids for the CH3-R hexapod from Lynxmotion.
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